Field of the Invention
The preset disclosure relates to a scintillator panel, a radiation detector including the scintillator panel, and methods for manufacturing the scintillator panel and the radiation detector.
Description of the Related Art
Flat panel detectors (FPDs) and the like used for radiography in medical practice and other fields convert radiation that has passed through an object into light in the scintillator layer therein and detect the light from the scintillator layer with a light-receiving element. For a scintillator layer that can efficiently transmit light generated therein, needle crystals of cesium iodide formed by vapor deposition are used. The needle crystals are separate from each other by voids formed therebetween, and the difference between the refractive index of cesium iodide (about 1.8) and the refractive index of air (1.0) causes the light generated in the cesium iodide needle crystals to repeat total reflection, thus guiding the light to the light-receiving element. Consequently, the modulation transfer function (MTF) of the radiation detector is increased. The term needle crystals used herein refer to crystals grown in one direction and is not limited by the shape of the tips of the crystals (hence, columnar crystals are included).
For forming needle crystals by vapor deposition, a method generally referred to as oblique incidence evaporation or oblique vapor deposition is known. Oblique vapor deposition is a method of vapor deposition performed such that the angle (incident angle 5) between the normal 11 to the deposition surface 6 of a substrate and the incident direction 54 of the particles 4 of the deposition material (particles of scintillator material in the present disclosure) is more than 0 degrees, as shown in FIG. 9. An effect of shadows 13 produced by tips of needle crystals 10, namely, shadowing effect, causes particles 4 of the deposition material not to directly reach an area between adjacent crystals, consequently forming voids 12. Since the size of the shadows 13 can be adjusted by varying the incident angle 5, the size (width) of the voids 12 can also be adjusted.
International Publication No. WO 2013-089015 discloses a method for producing a scintillator panel by oblique vapor deposition. In this method, a substrate and a deposition source are arranged so that a scintillator material can incident obliquely on a deposition surface of the substrate, and the material is deposited while the substrate is rotated in a direction 7. This method allows the scintillator material to incident on the needle crystals formed on the deposition surface in various directions, and accordingly enables each of the needle crystals to grow along the normal to the deposition surface.
Unfortunately, the oblique vapor deposition disclosed in the cited International Publication No. WO 2013-089015 does not allow the needle crystals to be aligned in a plane at the surface of the substrate.